THE QUARTERLY

JOURNAL OF SCIENCE.

JANUARY, 1867.

I. SIR CHARLES LYELL AND MODERN GEOLOGY.

Or late years the attention of a large number of geologists has been directed to an examination of the nature and potency of the causes of change now operating on the surface of the earth. This course of observation was first firmly trodden by Sir Charles Lyell; and now that we are reposing for a time after a series of controversies on subaerial forces, it may be useful to give a sketch of the services which have been rendered to science by the philosopher who, thirty-six years ago, founded the now dominant school of Geology.

In 1830 Sir Charles Lyell published the first volume of the first edition of the Principles of Geology.' As stated on the title-page, it was 66 an attempt to explain the former changes of the earth's surface by reference to causes now in action." This great work at once established Sir Charles Lyell's reputation as a philosophical geologist of the highest order; more than that, it produced the Uniformitarian' school of geology, to which belong nearly the whole of the distinguished geologists of the present day, who at that time were but students of the science. Mr. Darwin expects that the younger zoologists will hereafter confirm his theory of Natural Selection; but Sir Charles Lyell can say that the younger geologists of thirty years ago have done this for the doctrine of Uniformity. In fact, soon after its publication, Lyell's 'Principles became a household book; and although much that it contained met with opposition from some of the leading geologists of the day, that did not prevent the great body of their successors from accepting it as their guide and text-book in geological reasoning. The Royal Society also "crowned" the work by awarding a Royal Medal to its author the year after its completion (1834).

To future generations of geologists, Sir Charles Lyell's reputation will chiefly depend upon their estimate of the effect produced on the scientific world by the publication of the first edition of the Principles.' Even at this distance of time it is difficult to

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form a correct and impartial estimate of what geology would have been had the Principles' never been published. The chief design of the work was to uphold and strengthen the Huttonian doctrine of uniformity in the causes which have operated, and the phenomena which have been produced, throughout all geological time. The antagonistic doctrine of cataclysms was dominant, if not universally received, at the time of its publication, and is even now not quite extinct amongst some of the older geologists; although it is altogether ignored by those to whom in early days the 'Principles' has been a geological catechism. Still, the chief geologists of that day united in bearing testimony to the great value of the book, and may be useful to quote a few of the opinions then expressed by men whose writings are still referred to with respect.

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Dr. Whewell, in his History of the Inductive Sciences,' frequently discusses the Principles,' and in reference to causes of change he remarks that it may "be looked upon as the beginning of Geological Dynamics, at least among us. Such generalizations and applications as it contains give the most lively interest to a thousand observations respecting rivers and floods, mountains and morasses, which otherwise appear without aim or meaning."* The Rev. W. D. Conybeare, in his report on Geology to the second meeting of the British Association, says that it is "in itself sufficiently important to mark almost a new era in the progress of our science;" and Dr. Fitton considered it one of the most popular books, "and certainly one of the most valuable that has appeared since Mr. Playfair's well-known Illustrations of the Huttonian Theory." "+

Perhaps the most graceful allusion to the merits of the Principles' is contained in Mr. Poullett Scrope's dedication to Sir Charles Lyell of the second edition of his work on Volcanoes, published in 1862. This distinguished geologist then wrote, "When the first edition of this work [Volcanoes] saw the light, now seven-and thirty years ago, . you expressed a warmer interest in, and more agreement with, the views it contained than they met with from the bulk of our associates. It was an attempt to investigate one important class of the agencies of change now in operation on the earth's surface, and to trace their analogy, or rather identity, with those which have apparently prevailed through earlier geological periods-a portion, in fact, of the great task at which you have so long laboured, as respects the entire range of terrestrial phenomena, with an originality, persistence, and success that have placed you by common consent at the head of the followers of the science." This dedication was written only four years ago, and is on that account more valuable, as showing the estimation in * Op. cit., vol. iii., p. 552. Rep. Brit. Assoc.,' 1832, p. 406. Edinburgh Review,' vol. Ixix., No. 140, p. 406, 1839.

which so eminent a geologist, who has seen the full effects of the 'Principles,' holds that work and its author.

Although Dr. Whewell, Mr. Conybeare, and others united in recognizing the importance and merit of the Principles' in a general way, most of the geologists of five-and-thirty years ago also joined with them in declaring that Sir Charles Lyell went too far; that the doctrine of uniformity does not hold good when applied to remote epochs; but that, for instance, the metamorphic rocks were altered by agencies of far greater intensity than any that prevail at the present day. They contended that although the forces which formerly produced changes on the surface of the globe were in bygone times the same in kind as they are now, they were different in degree. Sir Charles Lyell, on the other hand, has persistently maintained that we have no evidence to warrant us in assuming those forces to have possessed greater intensity than at present during any geological period, and that until such evidence is discovered we have no right to attempt to explain past events by reference to causes of greater intensity than now operate at and beneath the surface of the earth. In the first chapter of the 'Principles,' Sir Charles Lyell quotes Hutton for the purpose of showing that geology is not concerned "with questions as to the origin of things," and is entirely distinct from cosmogony and cosmogonic speculations.

The science of Geology is, indeed, like every other science, a knowledge of phenomena and their causes; and no period can therefore be considered geologic that is not represented by rockmasses on some part of the present surface of the globe. No doubt there were pre-Laurentian periods; but at present we know nothing of them, and they cannot yet be considered to come within the scope of geological inquiry. The objection which has frequently been made to the doctrine of uniformity, that it assumes the eternity of the globe, is therefore of no value, for geologists do not attempt to speculate on the causes of phenomena of which they have no kind of knowledge.

It is unnecessary to enter into any argument respecting the doctrine of uniformity, as it is now practically acknowledged on all hands; but we would observe, that an examination of geological literature will show that while the terms "convulsion," "catastrophe," and the like were in common use previous to the year 1830, since that time they have been used with a gradually decreasing frequency; and a careful study of the progress of geological thought will likewise show that this result is almost entirely attributable to the publication of Sir Charles Lyell's 'Principles of Geology.'

It has, however, been assumed by some geologists of the present day, that the only claim on our respect which it could be pretended

that the Principles' possesses is founded on the supposition that the Idea of Uniformity originated with Sir Charles Lyell, and that as this supposition is incorrect, no special degree of merit should be attributed to Sir Charles for that particular work. Our own opinion is diametrically opposed to this, for according to our conception of the case the value of the Principles' lies chiefly in the proof it contains of Hutton's Theory of the Earth' being supported by positive evidence, instead of being a mere unsupported effort of the imagination. Sir Charles Lyell brought together in the Principles' a great mass of facts bearing on every phase of the theory, and this not in a mere superficial manner. Before the publication of this work, Hutton's Theory was to the great body of geologists nothing but the dream of an enthusiast; for ever afterwards it became a reality, and the theory of a philosopher.

The vexed questions of originality and priority are frequently the stumbling-blocks to a correct estimate of the services of great men. It has often happened that a great discovery has been made by one man, the importance and value of which have not been recognized until made manifest by another. The familiar case of the accidental discovery of Voltaic Electricity by Galvani, and the recognition of its importance by Volta, is an extreme instance; and the one under discussion, though differing from it in some essential respects (especially as regards accident), falls into the same category in others. Hutton, no doubt, was too far in advance of his age for his theory to be accepted by men of his generation, and it was characterized as premature by Dr. Whewell, even in 1837. How much longer it would have remained neglected had not Sir Charles Lyell written the 'Principles,' may to some extent be inferred by a reference to dates. Hutton's theory was first made public in 1788; from that time to the publication of the Principles of Geology' in 1830, a period of forty-two years, the progress made in Geological Dynamics is insignificant compared with the advance made during the thirty-six years which have since elapsed. We therefore endorse the opinion expressed by eminent men long ago, that Sir Charles Lyell's work was the beginning of a new era of progress in our science-the commencement, in fact, of a Rational Geology.

After scrutinizing the effects of existing causes of known intensity, as exhibited at the present day, Sir Charles Lyell was naturally led to examine the Tertiary deposits of different parts of Europe; and it was in tracing backwards the more and more complete disappearance of recent forms from Tertiary faunas that he conceived the idea of determining the relative age of these strata by the ratio which the recent species of Mollusca in their respective faunas bore to the extinct. Hence he proposed the now worldrenowned classification of Tertiary deposits into Eocene, Miocene, and Pliocene; and enunciated the scheme for their determination